Triangle Seminars
December 2008
Tue
16 Dec 2008
Tuck's incompressibility function: statistics for zeta zeros and eigenvalues
Michael Berry
(Bristol)
Abstract:
Tuck devised a function Q(x), associated with a function D(x), whose positivity guarantees the absence of complex zeros of D(x) close to the real x axis, and observed that large values of Q are very rare if D is associated with the Riemann zeros. In an unusual and challenging application of random-matrix theory with P Shukla, this is explained by studying the probability distribution P(Q) for functions D with N zeros corresponding to eigenvalues of the Gaussian unitary ensemble (GUE).
Tuck devised a function Q(x), associated with a function D(x), whose positivity guarantees the absence of complex zeros of D(x) close to the real x axis, and observed that large values of Q are very rare if D is associated with the Riemann zeros. In an unusual and challenging application of random-matrix theory with P Shukla, this is explained by studying the probability distribution P(Q) for functions D with N zeros corresponding to eigenvalues of the Gaussian unitary ensemble (GUE).
Posted by: brunel
Mon
15 Dec 2008
Virasoro constraints and decomposition formulas in matrix models
Alexander Alexandrov
(Imperial)
Fri
12 Dec 2008
Applied String Theory: Transport properties of holographic defects
Matthias Wapler
(Perimeter institute)
Abstract:
I will describe recent efforts in applying the AdS/CFT correspondence to Condensed Matter Physics. In particular, we study the charge transport properties of fields confined to a (2+1)-dimensional defect coupled to a (3+1) dimensional super-Yang-Mills theory at large-N_c and strong coupling, using AdS/CFT techniques applied to linear response theory.
I will describe recent efforts in applying the AdS/CFT correspondence to Condensed Matter Physics. In particular, we study the charge transport properties of fields confined to a (2+1)-dimensional defect coupled to a (3+1) dimensional super-Yang-Mills theory at large-N_c and strong coupling, using AdS/CFT techniques applied to linear response theory.
Posted by: QMW
Wed
10 Dec 2008
LHC and the Search for the Higgs Boson
Nick Evans
(University of Southampton)
Abstract:
The Large Hadron Collider is just beginning it's work as the highest energy proton proton collider ever made. After a brief introduction to the machine I will concentrate on it's main goal - the search for the Higgs boson. The Higgs is the missing particle from the Standard Model of particle physics which makes the model well behaved at high energy and generates particle mass. Something has to be there to do the job of the Higgs but there are hints of flaws in the simplest model that have led to many suggestions for new physics from particle compositeness to extra space-time dimensions.
The Large Hadron Collider is just beginning it's work as the highest energy proton proton collider ever made. After a brief introduction to the machine I will concentrate on it's main goal - the search for the Higgs boson. The Higgs is the missing particle from the Standard Model of particle physics which makes the model well behaved at high energy and generates particle mass. Something has to be there to do the job of the Higgs but there are hints of flaws in the simplest model that have led to many suggestions for new physics from particle compositeness to extra space-time dimensions.
Posted by: KCL
Wed
10 Dec 2008
Brownian motion and AdS/CFT
Jan de Boer
(University of Amsterdam)
Abstract:
TBA
TBA
Posted by: KCL
Wed
10 Dec 2008
Conformal Interfaces and String Symmetries
Costas Bachas
(ENS Paris)
Tue
9 Dec 2008
Random Matrices and Random Graphs
Uzy Smilansky
(Weizmann Institute)
Mon
8 Dec 2008
Deep Inelatsic Scattering in AdS/CFT
Anastasios Taliotis
(Ohio)
Abstract:
The total cross section for the scattering of a quark anti-quark dipole on a large nucleus at high energy is calculated. The system is studied within the framework of a strongly coupled N = 4 super Yang-Mills theory and the problem is solved using the AdS/CFT correspondence. The nucleus is modeled by a metric of a shock wave in AdS5. The expectation value of the Wilson loop (the dipole) is calculated by finding the extrema of the Nambu-Goto action for an open string attached to the quark and antiquark lines of the loop in the background of an AdS5 shock wave. Two physically meaningful extremal string configurations are found. For both solutions, the forward scattering amplitude N for the quark dipolenucleus scattering is found and is being investigated. The results are analyzed and compared with those in the literature. In particular for both solutions the saturation scale Qs (i.e. the scale where the partons densities inside the nucleus reach their maximum values) at high enough energy, becomes energy independent. In addition, the pomeron intercept that corresponds to a single graviton exchange is calculated and conjectured to be equal to aP =1.5.
The total cross section for the scattering of a quark anti-quark dipole on a large nucleus at high energy is calculated. The system is studied within the framework of a strongly coupled N = 4 super Yang-Mills theory and the problem is solved using the AdS/CFT correspondence. The nucleus is modeled by a metric of a shock wave in AdS5. The expectation value of the Wilson loop (the dipole) is calculated by finding the extrema of the Nambu-Goto action for an open string attached to the quark and antiquark lines of the loop in the background of an AdS5 shock wave. Two physically meaningful extremal string configurations are found. For both solutions, the forward scattering amplitude N for the quark dipolenucleus scattering is found and is being investigated. The results are analyzed and compared with those in the literature. In particular for both solutions the saturation scale Qs (i.e. the scale where the partons densities inside the nucleus reach their maximum values) at high enough energy, becomes energy independent. In addition, the pomeron intercept that corresponds to a single graviton exchange is calculated and conjectured to be equal to aP =1.5.
Posted by: IC
Thu
4 Dec 2008
Bubbling and AdS Solutions in string theory
Aristomenis Donos
(DESY)
Wed
3 Dec 2008
Generalizing topological A- and B-models
📍 London
Vid Stojevic
(Hamburg)
Abstract:
I will talk about my recent work (0801.1160, 0809.4034) on
generalizing the A- and B-models via the Alexandrov-Kontsevich-Schwarz-Zaboronsky (AKSZ) construction, in the context of both flux compactifications, and the doubled geometry of Hull.
I will talk about my recent work (0801.1160, 0809.4034) on
generalizing the A- and B-models via the Alexandrov-Kontsevich-Schwarz-Zaboronsky (AKSZ) construction, in the context of both flux compactifications, and the doubled geometry of Hull.
Posted by: KCL
Wed
3 Dec 2008
Quantum Strings in AdS4 x P3
Tristan McLoughlin
(Max Planck Institute)
Abstract:
There has been much recent interest in the proposed
duality between superstrings in the curved geometry AdS_4 x P3 and
three dimensional N=6 supersymmetric Chern-Simons theory –
a new, concrete, example of the holographic AdS/CFT correspondence.
This dual pair has additionally been conjectured to
be an integrable system in the planar limit.
In this talk I will discuss several classes of classical
strings moving in this background, and their quantum corrections,
as tools to probe the duality and to test the conjectured integrable
structure.
There has been much recent interest in the proposed
duality between superstrings in the curved geometry AdS_4 x P3 and
three dimensional N=6 supersymmetric Chern-Simons theory –
a new, concrete, example of the holographic AdS/CFT correspondence.
This dual pair has additionally been conjectured to
be an integrable system in the planar limit.
In this talk I will discuss several classes of classical
strings moving in this background, and their quantum corrections,
as tools to probe the duality and to test the conjectured integrable
structure.
Posted by: IC
Wed
3 Dec 2008
Deformations: from analysis to algera and back
Raphael Rouquier
(Oxford University)
Abstract:
We will introduce deformations of partial derivatives (Dunkl
operators) and discuss their actions on polynomial functions. This leads to various flavours of Hecke algebras and relates to the geometry of families of points in the plane. Eventually, this can be studied through microlocal analysis.
We will introduce deformations of partial derivatives (Dunkl
operators) and discuss their actions on polynomial functions. This leads to various flavours of Hecke algebras and relates to the geometry of families of points in the plane. Eventually, this can be studied through microlocal analysis.
Posted by: KCL
Tue
2 Dec 2008
Correlations of Characteristic Polynomials of Wigner Matrices
Holger Koesters
(Bielefeld)
Abstract:
The characteristic polynomials of random matrices from various random matrix ensembles have been investigated over the last few years. In this talk I will present some results
on the correlations of the characteristic polynomials of general Wigner matrices. It turns out that the well-known results for Gaussian Wigner matrices essentially continue to hold in this setting. This talk is partly based on joint work
with Friedrich Goetze.
The characteristic polynomials of random matrices from various random matrix ensembles have been investigated over the last few years. In this talk I will present some results
on the correlations of the characteristic polynomials of general Wigner matrices. It turns out that the well-known results for Gaussian Wigner matrices essentially continue to hold in this setting. This talk is partly based on joint work
with Friedrich Goetze.
Posted by: brunel
Mon
1 Dec 2008
Topos theory in the formulation of theories of physics
Chris Isham
(Imperial College)
November 2008
Thu
27 Nov 2008
On the perturbative structure of the S-matrix of massless particles
Paolo Benincasa
(Durham University)
Abstract:
The analysis of the singularities in the S-matrix of particles has shown
that perturbative structure field theories can be much simpler than what
Feynman diagrams tell us. In particular, there exist classes of theories
whose perturbative S-matrix is completely determined by a sub-set of its
singularities. At tree level this reflect with the existence of recursion
relations. At loop level, there are special singularities, the leading
singularities, which are believed to determine a class of theories which
N=4 SYM and N=8 supergravity belongs to. I will discuss both the tree and
loop level, with a particular attention on the leading singularity
technique and its application to the investigation of the perturbative N=8
supergravity.
The analysis of the singularities in the S-matrix of particles has shown
that perturbative structure field theories can be much simpler than what
Feynman diagrams tell us. In particular, there exist classes of theories
whose perturbative S-matrix is completely determined by a sub-set of its
singularities. At tree level this reflect with the existence of recursion
relations. At loop level, there are special singularities, the leading
singularities, which are believed to determine a class of theories which
N=4 SYM and N=8 supergravity belongs to. I will discuss both the tree and
loop level, with a particular attention on the leading singularity
technique and its application to the investigation of the perturbative N=8
supergravity.
Posted by: QMW
Wed
26 Nov 2008
Lagrangians for multiple M2 branes
📍 London
Neil Lambert
(KCL)
Wed
26 Nov 2008
Non-perturbative conformal invariance for time-dependent string backgrounds
Jean Alexandre
(King's College)
Abstract:
A specific configuration of the bosonic string is discussed, in
time-dependent backgrounds, which satisfies Weyl invariance to all
orders in the alpha'-expansion. Conformal invariance, valid in any space
time dimension, is based on the homogeneity (in time) of the Weyl-beta
functions which, using field redefinitions, can be made to vanish.
A specific configuration of the bosonic string is discussed, in
time-dependent backgrounds, which satisfies Weyl invariance to all
orders in the alpha'-expansion. Conformal invariance, valid in any space
time dimension, is based on the homogeneity (in time) of the Weyl-beta
functions which, using field redefinitions, can be made to vanish.
Posted by: IC
Wed
26 Nov 2008
TBA
Rudolf Tange
(The University of York)
Abstract:
TBA
TBA
Posted by: KCL
Tue
25 Nov 2008
Higgsing M2 worldvolume theories
Costis Papageorgakis
(TIFR, Mumbai)
Abstract:
I will be reviewing the details of a novel form of the Higgs mechanism,
present in the context of the Bagger-Lambert and ABJM proposals for the worldvolume
description of multiple parallel M2 branes. I will also discuss some of its implications
as well as describe related applications. The latter will focus on the determination of
four-derivative corrections to the Bagger-Lambert A_4-theory for all values
of the Chern-Simons level k
I will be reviewing the details of a novel form of the Higgs mechanism,
present in the context of the Bagger-Lambert and ABJM proposals for the worldvolume
description of multiple parallel M2 branes. I will also discuss some of its implications
as well as describe related applications. The latter will focus on the determination of
four-derivative corrections to the Bagger-Lambert A_4-theory for all values
of the Chern-Simons level k
Posted by: QMW
Mon
24 Nov 2008
Gluons, Spin Chains and String Theory
Nick Dorey
(DAMTP, Cambridge)
Fri
21 Nov 2008
London Mathematical Society Graduate Student Meeting
📍 London
Neil Lambert. David Tong.
Abstract:
Neil Lambert (KCL) 'From D-branes to M-branes', David Tong (DAMTP) 'Quantum vortex strings' plus several presentations by PhD students on their work. Ends at 14:15. See www.mth.kcl.ac.uk/'tilde'anderl/LMSpremeeting/
Neil Lambert (KCL) 'From D-branes to M-branes', David Tong (DAMTP) 'Quantum vortex strings' plus several presentations by PhD students on their work. Ends at 14:15. See www.mth.kcl.ac.uk/'tilde'anderl/LMSpremeeting/
Posted by: KCL
Fri
21 Nov 2008
London Mathematical Society Annual Meeting
📍 London
Graeme Segal. Michael Green.
Abstract:
Graeme Segal FRS (Oxford) 'Noncommutative geometry and quantum field theory' and Michael Green FRS (Cambridge) '2007 Naylor Lecture: Some dualities of string theory and quantum gravity'. Ends at 18:00. See www.mth.kcl.ac.uk/'tilde'anderl/LMSpremeeting/
Graeme Segal FRS (Oxford) 'Noncommutative geometry and quantum field theory' and Michael Green FRS (Cambridge) '2007 Naylor Lecture: Some dualities of string theory and quantum gravity'. Ends at 18:00. See www.mth.kcl.ac.uk/'tilde'anderl/LMSpremeeting/
Posted by: KCL
Thu
20 Nov 2008
Dynamical supersymmetry breaking, duality and unification
Valentin V. Khoze
(Durham University)
Wed
19 Nov 2008
Supergravity and ''exceptional'' generalised geometry
📍 London
Daniel Waldram
(IC)
Wed
19 Nov 2008
Complexified classical mechanics - an introduction
Daniel Hook
(Imperial College London)
Abstract:
Several recent papers have investigated the extention of classical PT-Symmetric Hamiltonians to the classical domain. This approach to classical mechanics will be introduced as a generalisation of the familiar classical mechanics learnt at high school. The properties of these systems are often surprising and specific graphical studies can be quite beautiful. Familiar classical systems will be studied and brand new results will be presented including an exploration of chaotic systems.
Several recent papers have investigated the extention of classical PT-Symmetric Hamiltonians to the classical domain. This approach to classical mechanics will be introduced as a generalisation of the familiar classical mechanics learnt at high school. The properties of these systems are often surprising and specific graphical studies can be quite beautiful. Familiar classical systems will be studied and brand new results will be presented including an exploration of chaotic systems.
Posted by: KCL
Wed
19 Nov 2008
Higgsing Worldvolume M2 Theories
Constantinos Papageorgakis
(TIFR, Mumbai)
Abstract:
I will be reviewing the details of a novel form of the Higgs mechanism, present in the context of the Bagger-Lambert and ABJM proposals for the worldvolume description of multiple parallel M2 branes. I will also discuss some of its implications as well as describe related applications. The latter will focus on the determination of four-derivative corrections to the Bagger-Lambert A_4-theory for all values of the Chern-Simons level k.
I will be reviewing the details of a novel form of the Higgs mechanism, present in the context of the Bagger-Lambert and ABJM proposals for the worldvolume description of multiple parallel M2 branes. I will also discuss some of its implications as well as describe related applications. The latter will focus on the determination of four-derivative corrections to the Bagger-Lambert A_4-theory for all values of the Chern-Simons level k.
Posted by: IC
Tue
18 Nov 2008
Integrable models from PT-symmetric deformations
Andreas Fring
(City University London)
Abstract:
I will give a brief account of some examples of non-Hermitian Hamiltonian systems with real spectra, which have appeared in the literature over the last four decades. I will discuss the spectral properties of these type of Hamiltonians and explain how their reality results from PT-symmetry, quasi-Hermiticity, pseudo-Hermiticity
or supersymmetry. Subsequently I review the general technicalities needed to formulate a consistent quantum mechanical system in this context by constructing an appropriate metric and domain. I will provide
some Lie algebraic examples.
Taking PT-symmetry as a guiding principle one may construct
deformations of integrable models, such as Calogero-Moser-Sutherland models, the Korteweg-deVries or Burgers equation. It turns out that some of these deformations are supersymmetry preserving. Others even leave the integrabilty in tact and therefore lead to new types
of integrable system.
I will give a brief account of some examples of non-Hermitian Hamiltonian systems with real spectra, which have appeared in the literature over the last four decades. I will discuss the spectral properties of these type of Hamiltonians and explain how their reality results from PT-symmetry, quasi-Hermiticity, pseudo-Hermiticity
or supersymmetry. Subsequently I review the general technicalities needed to formulate a consistent quantum mechanical system in this context by constructing an appropriate metric and domain. I will provide
some Lie algebraic examples.
Taking PT-symmetry as a guiding principle one may construct
deformations of integrable models, such as Calogero-Moser-Sutherland models, the Korteweg-deVries or Burgers equation. It turns out that some of these deformations are supersymmetry preserving. Others even leave the integrabilty in tact and therefore lead to new types
of integrable system.
Posted by: KCL
Mon
17 Nov 2008
Towards noncommutative toric geometry
Alistair Craw
(Glasgow)
Abstract:
Toric varieties have proved to be a fabulous testing ground for questions in algebraic geometry and string theory for many years. I will describe work in progress with Greg Smith that lays the foundation for a noncommutative analogue. As applications, I will provide a multigraded version of Beilinson's theorem on the derived category of projective space and I will propose a concrete link to dimer models.
Toric varieties have proved to be a fabulous testing ground for questions in algebraic geometry and string theory for many years. I will describe work in progress with Greg Smith that lays the foundation for a noncommutative analogue. As applications, I will provide a multigraded version of Beilinson's theorem on the derived category of projective space and I will propose a concrete link to dimer models.
Posted by: IC
Wed
12 Nov 2008
A bound state in a conformal field theory with continuous spectrum and deep throat D-branes
Jan Troost
(ENS Paris)
Wed
12 Nov 2008
Gauge/Gravity Duality in Supersymmetric and Non-Supersymmetric Vacua
Riccardo Argurio
(Universite Libre de Bruxelles)
Abstract:
I start by giving a brief introduction to the duality between string theory and gauge theories. I will underscore the dictionary between geometrical data on the string side, and dynamical effects on the gauge theory side. Different kinds of fractional branes lead to different IR dynamics, such as confinement, Coulomb branches, and runaway or metastable supersymmetry breaking. I then review a model, D3-branes on the orbifold of the conifold, that displays all of the above behaviors. Of particular interest is the case when different fractional branes are present at the same time, leading to a rich dynamical interplay.
I start by giving a brief introduction to the duality between string theory and gauge theories. I will underscore the dictionary between geometrical data on the string side, and dynamical effects on the gauge theory side. Different kinds of fractional branes lead to different IR dynamics, such as confinement, Coulomb branches, and runaway or metastable supersymmetry breaking. I then review a model, D3-branes on the orbifold of the conifold, that displays all of the above behaviors. Of particular interest is the case when different fractional branes are present at the same time, leading to a rich dynamical interplay.
Posted by: KCL
Mon
10 Nov 2008
Principia 3-algebraica
Paul de Medeiros
(Edinburgh)
Abstract:
A precise method for relating quite general kinds of metric 3-algebras with metric Lie algebras and their unitary representations will be described. Several special cases of this construction will be highlighted, that apply to certain types of superconformal field theories dual to M2-brane configurations. Recognition of M-theoretic properties in terms of Lie-algebraic data will be noted in passing. Some remarks will be made on the general structure of metric Lie 3-algebras, which describe maximally supersymmetric Bagger-Lambert theories.
A precise method for relating quite general kinds of metric 3-algebras with metric Lie algebras and their unitary representations will be described. Several special cases of this construction will be highlighted, that apply to certain types of superconformal field theories dual to M2-brane configurations. Recognition of M-theoretic properties in terms of Lie-algebraic data will be noted in passing. Some remarks will be made on the general structure of metric Lie 3-algebras, which describe maximally supersymmetric Bagger-Lambert theories.
Posted by: IC
Wed
5 Nov 2008
The Classification of Highly Supersymmetric Supergravity Solutions
📍 London
Jan Gutowski
(KCL)
Abstract:
Spinorial geometry techniques provide new ways to analyze
supersymmetric solutions of supergravity theories in a systematic fashion. I will describe how one can apply these methods to classify solutions of type IIB supergravity which preserve large amounts of supersymmetry. In particular, this provides a proof that solutions preserving exactly 31/32 of the supersymmetry do not exist, which resolves a long-standing open question.
Spinorial geometry techniques provide new ways to analyze
supersymmetric solutions of supergravity theories in a systematic fashion. I will describe how one can apply these methods to classify solutions of type IIB supergravity which preserve large amounts of supersymmetry. In particular, this provides a proof that solutions preserving exactly 31/32 of the supersymmetry do not exist, which resolves a long-standing open question.
Posted by: KCL
Wed
5 Nov 2008
QCD-like properties of anomalous dimensions in AdS/CFT
Valentina Forini
(AEI, Potsdam)
Abstract:
We consider the large spin expansions of anomalous dimensions for twist
operators in N=4 SYM and their AdS counterpart in terms of energies of
some classical string configurations. Evidence is given, both at weak
and strong coupling in perturbation theory, that they respect a
generalization of the property known in QCD as Gribov-Lipatov
reciprocity.
We consider the large spin expansions of anomalous dimensions for twist
operators in N=4 SYM and their AdS counterpart in terms of energies of
some classical string configurations. Evidence is given, both at weak
and strong coupling in perturbation theory, that they respect a
generalization of the property known in QCD as Gribov-Lipatov
reciprocity.
Posted by: IC
Wed
5 Nov 2008
CANCELLED
Thanasis Fokas
(Cambridge University)
Abstract:
The seminar had to be cancelled, but will be held next term.
The seminar had to be cancelled, but will be held next term.
Posted by: KCL
Tue
4 Nov 2008
Expansion of cold atoms in the presence of disorder
Boris Shapiro
(Israel Institute of Technology)
Abstract:
I will discuss the expansion of a Bose-Einstein condensate, released from a harmonic trap, in the presence of a random potential. The potential causes scattering of the condensate, preventing its free propagation. Under appropriate conditions some part of the condensate will get stuck (Anderson localization), whereas the rest will diffuse away. Expansion
of a cold Fermi gas will be also discussed.
I will discuss the expansion of a Bose-Einstein condensate, released from a harmonic trap, in the presence of a random potential. The potential causes scattering of the condensate, preventing its free propagation. Under appropriate conditions some part of the condensate will get stuck (Anderson localization), whereas the rest will diffuse away. Expansion
of a cold Fermi gas will be also discussed.
Posted by: brunel
Mon
3 Nov 2008
Holonomy, Berry Phase, and Supersymmetry
David Tong
(Cambridge)
Abstract:
As parameters in quantum mechanics are slowly varied, states
undergo a non-Abelian holonomy known as Berry phase. I will review the ideas behind the Berry phase and explain how supersymmetry imposes restrictions on the holonomy. The associated non-Abelian gauge connections must obey certain first order equations which are related to the self-dual
Yang-Mills equations, specifically the Hitchin equations, tt star equations, and Bogomolnyi equations. I will end by showing how one can build a BPS 't Hooft-Polyakov monopole in the lab.
As parameters in quantum mechanics are slowly varied, states
undergo a non-Abelian holonomy known as Berry phase. I will review the ideas behind the Berry phase and explain how supersymmetry imposes restrictions on the holonomy. The associated non-Abelian gauge connections must obey certain first order equations which are related to the self-dual
Yang-Mills equations, specifically the Hitchin equations, tt star equations, and Bogomolnyi equations. I will end by showing how one can build a BPS 't Hooft-Polyakov monopole in the lab.
Posted by: IC
October 2008
Wed
29 Oct 2008
Higher-loop amplitudes in Maximal Supergravity and String Theory
📍 London
Pierre Vanhove
(Saclay)
Abstract:
We will describe the recent progresses in the computation of
four-graviton amplitudes at higher-loop order in maximal supergravity and string theory in various dimensions.
We will discuss the constraints from dualities and the extended supersymmetry on the structure of the amplitudes. We will explain that the cross-symmetry of gravity, maximal supersymmetry, and the constraints from higher dimensions play an important role in the improved ultraviolet behaviour of maximal supergravity in four dimensions.
We will describe the recent progresses in the computation of
four-graviton amplitudes at higher-loop order in maximal supergravity and string theory in various dimensions.
We will discuss the constraints from dualities and the extended supersymmetry on the structure of the amplitudes. We will explain that the cross-symmetry of gravity, maximal supersymmetry, and the constraints from higher dimensions play an important role in the improved ultraviolet behaviour of maximal supergravity in four dimensions.
Posted by: KCL
Wed
29 Oct 2008
The SU(2) X SU(2) sector of type IIA string theory on AdS4 X CP3
Marta Orselli
(Neils Bohr Institute)
Abstract:
I will examine the string dual of the recently constructed N = 6 superconformal Chern-Simons theory
of Aharony, Bergman, Jafferis and Maldacena (ABJM theory). In particular I will focus on the SU(2)X
SU(2) sector. I will derive the full magnon dispersion relation and compare it to recently found results for ABJM theory at weak coupling.
Then I will consider finite-size corrections to the energy of string states in the
R X S2 X S2 subspace of AdS4 X CP3 with an angular momentum J on CP3 being large, using two different approaches.
I will compare the results with the recently proposed all-loop Bethe ansatz of Gromov and Vieira.
I will examine the string dual of the recently constructed N = 6 superconformal Chern-Simons theory
of Aharony, Bergman, Jafferis and Maldacena (ABJM theory). In particular I will focus on the SU(2)X
SU(2) sector. I will derive the full magnon dispersion relation and compare it to recently found results for ABJM theory at weak coupling.
Then I will consider finite-size corrections to the energy of string states in the
R X S2 X S2 subspace of AdS4 X CP3 with an angular momentum J on CP3 being large, using two different approaches.
I will compare the results with the recently proposed all-loop Bethe ansatz of Gromov and Vieira.
Posted by: IC
Wed
29 Oct 2008
On quantum field theory with deformed Poincare symmetry
Charles Young
(Durham University)
Abstract:
There exists a family of deformations of Minkowski spacetime, and its Poincare symmetries, parameterized by a mass-scale
kappa. I will discuss some recent work in which ideas from the theory of quantum groups are applied to the problem of formulating kappa-deformed quantum field theory.
There exists a family of deformations of Minkowski spacetime, and its Poincare symmetries, parameterized by a mass-scale
kappa. I will discuss some recent work in which ideas from the theory of quantum groups are applied to the problem of formulating kappa-deformed quantum field theory.
Posted by: KCL
Thu
23 Oct 2008
TBA
Daniel Jafferis
(Rutgers)
Thu
23 Oct 2008
More on Four-point Functions of 1/2-BPS operators in the AdS/ CFT Correspondence
Linda Uruchurtu
(Cambridge)
Abstract:
In this talk I will describe the computation of the four-point function of two weight-2 and two weight-n 1/2-BPS operators at large N and at strong 't Hooft coupling, using the supergravity approximation. I will then discuss the results in the light of the AdS/CFT correspondence.
In this talk I will describe the computation of the four-point function of two weight-2 and two weight-n 1/2-BPS operators at large N and at strong 't Hooft coupling, using the supergravity approximation. I will then discuss the results in the light of the AdS/CFT correspondence.
Posted by: QMW
Wed
22 Oct 2008
Towards Realistic String Vacua
📍 London
Joe Conlon
(Oxford)
Abstract:
I describe work aimed at combining the advances in moduli stabilisation and supersymmetry breaking with that in building D-brane models with realistic chiral matter spectra. The framework is models of D3/D7 branes at del Pezzo singularities embedded in the LARGE volume scenario of moduli stabilisation. I describe the general phenomenological properties that emerge and discuss the difficulties in computing visible sector soft terms.
I describe work aimed at combining the advances in moduli stabilisation and supersymmetry breaking with that in building D-brane models with realistic chiral matter spectra. The framework is models of D3/D7 branes at del Pezzo singularities embedded in the LARGE volume scenario of moduli stabilisation. I describe the general phenomenological properties that emerge and discuss the difficulties in computing visible sector soft terms.
Posted by: KCL
Wed
22 Oct 2008
String Creation and Effective Field Theory
Janet Hung
(DAMTP, Cambridge)
Abstract:
We will discuss the missing pieces in the understanding of the
effective field theory description of string creation, the S-dual of the
Hanany-Witten effect, both in the open and closed string picture. We
explain the origin of a crucial bare Chern-Simons term, that used to be
added in by hand for consistency. Finally we summarize the remaining
unsettled issues, concerning the need to modify the DBI action and the
interpretation of the bare term in M-theory.
We will discuss the missing pieces in the understanding of the
effective field theory description of string creation, the S-dual of the
Hanany-Witten effect, both in the open and closed string picture. We
explain the origin of a crucial bare Chern-Simons term, that used to be
added in by hand for consistency. Finally we summarize the remaining
unsettled issues, concerning the need to modify the DBI action and the
interpretation of the bare term in M-theory.
Posted by: IC
Wed
22 Oct 2008
Special polynomials associated with rational solutions of Painleve equations
Peter Clarkson
(University of Kent)
Abstract:
In this talk I shall discuss special polynomials associated with rational solutions for the Painleve equations.
The Painleve equations (PI-PVI) are six nonlinear ordinary
differential equations that have been the subject of much interest in the past thirty years, which have arisen in a variety of physical applications. Further they may be thought of as nonlinear special functions and arise as symmetry reductions of soliton equations which are solvable by the inverse scattering method, such as the Korteweg-de Vries, Boussinesq and nonlinear Schroedinger equations. Rational solutions of the Painleve equations are expressible in terms of the logarithmic derivative of certain special polynomials. For PII these polynomials are known as the Yablonskii-Vorobev polynomials, first derived in the 1960's by Yablonskii and Vorob'ev. The locations of the roots of these polynomials is shown to have a highly regular triangular structure in the complex plane. The analogous special polynomials associated with rational solutions of PIII, PIV and PV are described and it is shown that their roots also have a highly regular structure.
In this talk I shall discuss special polynomials associated with rational solutions for the Painleve equations.
The Painleve equations (PI-PVI) are six nonlinear ordinary
differential equations that have been the subject of much interest in the past thirty years, which have arisen in a variety of physical applications. Further they may be thought of as nonlinear special functions and arise as symmetry reductions of soliton equations which are solvable by the inverse scattering method, such as the Korteweg-de Vries, Boussinesq and nonlinear Schroedinger equations. Rational solutions of the Painleve equations are expressible in terms of the logarithmic derivative of certain special polynomials. For PII these polynomials are known as the Yablonskii-Vorobev polynomials, first derived in the 1960's by Yablonskii and Vorob'ev. The locations of the roots of these polynomials is shown to have a highly regular triangular structure in the complex plane. The analogous special polynomials associated with rational solutions of PIII, PIV and PV are described and it is shown that their roots also have a highly regular structure.
Posted by: KCL
Tue
21 Oct 2008
A Random Matrix Theory of Decoherence on Qubits
Carlos Pineda
(Potsdam)
Abstract:
We present a model to study decoherence on non–interacting qubits. Single qubit decoherence (as measured by purity) is obtained in linear response. Two qubit decoherence is solved using the spectator configuration. Entanglement evolution is considered. The n-qubit case is studied using weaker
assumptions. Various results are exemplified using a kicked spin chain as a toy model.
We present a model to study decoherence on non–interacting qubits. Single qubit decoherence (as measured by purity) is obtained in linear response. Two qubit decoherence is solved using the spectator configuration. Entanglement evolution is considered. The n-qubit case is studied using weaker
assumptions. Various results are exemplified using a kicked spin chain as a toy model.
Posted by: brunel
Wed
15 Oct 2008
Unfolding of higher order exceptional points in a PT-symmetric Bose-Hubbard model
Eva-Maria Graefe
(Technische Universitaet Kaiserslautern)
Abstract:
We study an N-particle, two-mode Bose-Hubbard system, modelling a Bose-Einstein condensate in a double-well potential. By introducing effective complex energies to the modes we describe a coupling to a continuum. The eigenvalues of the resulting non-Hermitian matrix model are in general complex where the imaginary parts (resonance widths) describe the decay rate into the continuum.
In dependence on the parameters the spectrum shows an intricate structure of exceptional points, at which two or more eigenvalues as well as the corresponding eigenstates are degenerate. In the present talk the effect of the interplay between the particle interaction and the non-Hermiticity on the spectrum is analysed, drawing special attention to the occurrence and unfolding of exceptional points. Some peculiarities are clarified using perturbational methods.
We study an N-particle, two-mode Bose-Hubbard system, modelling a Bose-Einstein condensate in a double-well potential. By introducing effective complex energies to the modes we describe a coupling to a continuum. The eigenvalues of the resulting non-Hermitian matrix model are in general complex where the imaginary parts (resonance widths) describe the decay rate into the continuum.
In dependence on the parameters the spectrum shows an intricate structure of exceptional points, at which two or more eigenvalues as well as the corresponding eigenstates are degenerate. In the present talk the effect of the interplay between the particle interaction and the non-Hermiticity on the spectrum is analysed, drawing special attention to the occurrence and unfolding of exceptional points. Some peculiarities are clarified using perturbational methods.
Posted by: KCL
Wed
15 Oct 2008
Gluon Scattering in N=4 Super-Yang-Mills Theory from Weak to Strong Coupling
📍 London
Lance Dixon
(SLAC)
Abstract:
Scattering amplitudes in N=4 super-Yang-Mills theory can be defined in dimensional regularization near four dimensions, and have a number of remarkable features. There is good evidence for an exact, all-loop formula for the planar four- and five-point scattering amplitudes in terms of four functions of the coupling alone, one of which is the cusp anomalous dimension. For six gluons this particular formula fails. However, for the 'MHV' helicity configuration, an equivalence to a Wilson line expectation value on a hexagon persists at two loops, as does a certain 'dual conformal invariance'. These properties are connected to features of string propagation in AdS(5) x S5, in particular T duality.
Scattering amplitudes in N=4 super-Yang-Mills theory can be defined in dimensional regularization near four dimensions, and have a number of remarkable features. There is good evidence for an exact, all-loop formula for the planar four- and five-point scattering amplitudes in terms of four functions of the coupling alone, one of which is the cusp anomalous dimension. For six gluons this particular formula fails. However, for the 'MHV' helicity configuration, an equivalence to a Wilson line expectation value on a hexagon persists at two loops, as does a certain 'dual conformal invariance'. These properties are connected to features of string propagation in AdS(5) x S5, in particular T duality.
Posted by: KCL
Wed
15 Oct 2008
Dual superconformal invariance from AdS5 x S5
📍 London
Riccardo Ricci
(Imperial)
Abstract:
In this talk we discuss 2d duality transformations in the classical AdS5 x S5 superstring and their effect on the integrable structure. We will see that combining T-duality along four directions in Poincare parametrization of AdS5 with a similar duality transformation on some of the fermionic variables maps the superstring action into itself. One implication is that, after duality, the superstring has a 'dual' superconformal symmetry group. Furthermore this dual superconformal symmetry can be seen as a consequence of the integrability of the superstring. This will also suggest that the dual superconformal charges correspond to non-local charges of the original model before T-duality.
In this talk we discuss 2d duality transformations in the classical AdS5 x S5 superstring and their effect on the integrable structure. We will see that combining T-duality along four directions in Poincare parametrization of AdS5 with a similar duality transformation on some of the fermionic variables maps the superstring action into itself. One implication is that, after duality, the superstring has a 'dual' superconformal symmetry group. Furthermore this dual superconformal symmetry can be seen as a consequence of the integrability of the superstring. This will also suggest that the dual superconformal charges correspond to non-local charges of the original model before T-duality.
Posted by: KCL
Thu
9 Oct 2008
Saturation in Deep Inelastic Scattering from AdS/CFT
Lorenzo Cornalba
(Milan Bicocca)
Abstract:
We analyze interactions at high energies in AdS spaces, at large and small AdS curvatures. We then use the results to analyze deep inelastic scattering at small Bjorken x, using the approximate conformal invariance of QCD at high energies. Hard pomeron exchanges are resummed eikonally, restoring unitarity at large values of the phase shift in the dual AdS geometry. At weak coupling this phase is imaginary, corresponding to a black disk in AdS. In this saturated regime, cross sections exhibit geometric scaling and have a simple universal form, which we test against available experimental data for the proton structure function F2(x,Q2). We predict, in particular, the dependence of the cross section on the scaling variable (Q/Qs)2 in the deeply saturated region, where Qs is the usual saturation scale. We find agreement with current data on F2 in the kinematical region defined by Q2 between 0.5 and 10 GeV2, x less than 10E(-2), with an average 6 per cent accuracy. We conclude by discussing the relation of our approach with the commonly used dipole formalism.
We analyze interactions at high energies in AdS spaces, at large and small AdS curvatures. We then use the results to analyze deep inelastic scattering at small Bjorken x, using the approximate conformal invariance of QCD at high energies. Hard pomeron exchanges are resummed eikonally, restoring unitarity at large values of the phase shift in the dual AdS geometry. At weak coupling this phase is imaginary, corresponding to a black disk in AdS. In this saturated regime, cross sections exhibit geometric scaling and have a simple universal form, which we test against available experimental data for the proton structure function F2(x,Q2). We predict, in particular, the dependence of the cross section on the scaling variable (Q/Qs)2 in the deeply saturated region, where Qs is the usual saturation scale. We find agreement with current data on F2 in the kinematical region defined by Q2 between 0.5 and 10 GeV2, x less than 10E(-2), with an average 6 per cent accuracy. We conclude by discussing the relation of our approach with the commonly used dipole formalism.
Posted by: QMW
Wed
8 Oct 2008
Novel structures in scattering amplitudes
📍 London
Gabriele Travaglini
(Queen Mary)
Wed
8 Oct 2008
More on four-point functions of 1/2 BPS operators in the AdS/CFT
Linda Uruchurtu
(DAMTP Cambridge)
Abstract:
In this talk I will describe the computation of the four-point function of two weight-2 and two weight-n 1/2-BPS operators at large N and at strong t Hooft coupling, using the supergravity approximation. I will then discuss the result in the light of the AdS/CFT correspondence.
In this talk I will describe the computation of the four-point function of two weight-2 and two weight-n 1/2-BPS operators at large N and at strong t Hooft coupling, using the supergravity approximation. I will then discuss the result in the light of the AdS/CFT correspondence.
Posted by: IC
September 2008
Mon
15 Sep 2008
Green-Schwarz action for Type IIA strings on AdS(4) x CP3
Bogdan Stefanski
(MIT, LNS and Imperial College)
Wed
3 Sep 2008
Holographic Hydrodynamics at Finite Coupling
Aninda Sinha
(Perimeter Institute)